Conventional approaches to high temperature sensing employ blackbody radiation heat flux gauges, such as infrared sensing devices that rely on blackbody radiation science to measure the radiation and temperature of an object without physically touching it. For a lower but most common temperature range of 200° K-800° K, the physical phenomena exploited to sense this radiation is the thermoelectric effect (also known as the Seebeck effect, or Peltier effect) in which case an increase in temperature of a material creates an increase in its voltage in reference to the previous temperature of the object. In the case that this heat input is radiation, and not conduction or convection, the discrete electronic device used is a thermopile, which practically isolates the sensing element from the surrounds which may conduct or convect heat to it, and only allows radiation to enter from a transparent window. This conventional approach converts minute heat input of a small magnitude of photons into a measurable voltage, which defines the output signal used to calculate the temperature or irradiance on the sensor window. For the high temperature case, specifically 800° K-2300° K (980° F.-3680° F.), such devices may not be suitable due to the sheer magnitude of the radiant heat flux increasing many orders of magnitude, to the point of saturating the thermopile sensors.
Relevant background technology for conventional thermal measurement embrace Planck's Law of thermal radiation energy distributions over the electromagnetic wavelength spectrum as a function of an emitter's temperature. Such optical sensing systems measure an objects radiant heat flux without physically contacting it, and derive its temperature based on thermal radiation relations. These systems include radiometers, infrared thermometers, pyrometers, bolometer, thermographic cameras, and other infrared sensing device that relies on blackbody radiation science, and have been developed widely over the last century. These devices generally quantify an object's temperature by measuring the magnitude of radiation present at a certain wavelength range. The specific range used depends on the expected temperature range of the measured object, as the thermal radiation emission can vary significantly with temperature.